When it is desired to charge a bag with an article to be packaged, it is known from experience that however wide the mouth of the bag may be opened, the article tends to spill; thus, it has been common practice to use a nozzle or hopper to satisfactorily charge bags with articles. For example, U.S. Pat. No. 2,833,097 discloses an apparatus designed to place a stack of bags in a bag storage box, remove the endmost bag from the stack by a vacuum cup, and put the removed bag over a suspended hopper, and U.S. Pat. No. 3,945,173 discloses an apparatus designed to open a bag placed on a table by sucking the mouth of the bag by a pair of vacuum cups, insert a split circular member into the opened mouth to maintain the bag mouth in the opened state by means of said round member, and put said bag over a suspended hopper.
U.S. Pat. No. 2,833,097 states that the mouth of the endmost bag is opened when said bag is separated from the rest of the bags stacked in the bag storage box when it is sucked by the vacuum cup. However, such bags cannot always be completely opened; failures in opening bags take place.
On the other hand, since U.S. Pat. No. 3,945,173 is adapted to open bags by sucking the opposite sides of the mouth of a bag by a pair of vacuum cups and separating the vacuum cups from each other to open the mouth, the number of failures in opening bags is certainly reduced. However, plastic films which form bags tend to be charged with electricity on the one hand and on the other hand negative pressure tends to be produced in bags when they are forced to open quickly, with the result that the bag surface often tends to separate from the vacuum cups. Therefore, said two known apparatuses have a drawback in that they cannot reliably put bags over the hopper unless the working efficiency is decreased.